1. Field of the Invention
The present invention relates to an angle rotor and a culture/centrifugal tube used in the angle rotor.
2. Description of Related Art
High-speed centrifuges are available in small sizes and with cooling functions and are used in a variety of fields, such as the medical, chemical, pharmaceutical, and genetic engineering fields. Disposable culture centrifuge tubes are used in the centrifuges.
One type of centrifuge includes an angle rotor and a motor that produces drive force that rotates the angle rotor. A culture centrifuge tube filled with a sample liquid to be separated is mounted in the angle rotor, and the motor rotates the angle rotor. This type of centrifuge can rotate at maximum speeds of 5,000 to 14,000 RPMs. Some centrifuges can reach maximum speeds of up to 25,000 RPMs. Angle rotors are produced for various uses and are rotated either under atmospheric pressure or within a vacuum.
Here are some examples of angle rotor models on the market today: R12A5, R10A2, T11A21, and T9A31 produced by Hitachi Koki Co., Ltd. and TA22 and TA23 produced by Tomy Digital Biology Co., Ltd. These angle rotors are normally made from an aluminum alloy. To produce an angle rotor, a block of the aluminum alloy is machined with accommodation holes for accommodating the culture centrifuge tubes and with a drive shaft hole for inserting the drive shaft of the drive motor.
Culture centrifuge tubes supported in the angle rotor are sample tubes used in centrifugal separation and are alternatively referred to as culture/centrifugal tubes, tissue culture/centrifugal tubes, centrifugal tubes, or tissue culture/centrifugal tubes (TC tubes). A variety of culture/centrifugal tubes, such as those produced by Sumitomo Bakelite Co., Ltd., Asahi Technoglass Corporation, and KK Ashisato, are on the market. Culture centrifugal tubes, including the cap, are made from a plastic material such as polypropylene or polystyrene using injection technology. Because culture/centrifugal tubes are disposable and used in large quantities, they need to be inexpensive. The culture/centrifugal tubes are used as a container for cell culture and then inserted in the angle rotor as is to collect the cultivated cells.
FIG. 1 shows a configuration of a conventional angle rotor 101. The angle rotor 101 is driven by a motor (not shown) to rotate around a rotation axis B—B. The angle rotor 101 is formed with an accommodation hole 110a that slants at a predetermined angle with respect to the rotation axis B—B. The accommodation hole 110a is for accommodating a culture/centrifugal tube 120. As will be described later, the culture/centrifugal tube 120 is for use in a centrifuge and includes a tube 121 and a cap 122. The accommodation hole 110a includes a tube accommodation portion 110f and a step 110g. The tube accommodation portion 110f and the step 110g are continuous with each other. The tube accommodation portion 110f accommodates the tube 121 and the step 100g accommodates the cap 122.
As shown in FIG. 2, the culture/centrifugal tube 120 includes the tube 121 and the cap 122. The tube 121 and the cap 122 are made from plastic. One end of the tube 121 is closed and defines a bottom 121A. The other end defines an opening portion 121B. A spiral-shaped male screw portion 121C is formed near the opening portion 121B. The cap 122 is provided for covering the opening portion 121B and includes a disk portion 122A and an annular portion 122B. The annular portion 122B extends from the outer periphery of one surface 122C of the disk portion 122A in the axial direction of the disk portion 122A. The inner peripheral surface of the annular portion 122B is formed with a spiral-shaped female screw portion 122F. An annular lip 122J extends from the surface 122C of the disk portion 122A. The annular lip 122J has a smaller diameter than the outer periphery of the disk portion 122A.
The cap 122 is placed over the opening portion 121B of the tube 121 and twisted to engage the male screw 121C with the female screw 122F. By this, the cap 122 covers the opening portion 121B of the tube 121 with the annular lip 122J of the cap 122 in intimate contact with the opening portion 121B. Therefore, the cap 122 seals the opening portion 121B of the tube 121. As shown in FIG. 1, the culture/centrifugal tube 120 is then inserted into the accommodation hole 110a of the angle rotor 101. Centrifugal separation is then performed by rotating the angle rotor 101.
As shown in FIG. 2, the male screw 121C of the tube 121 is provided at a position that is separated from an open end 121E of the opening portion 121B. Also, the female screw portion 122F is provided at a position that is separated from the position where the annular portion 122B and the disk portion 122A of the cap 122 are connected to each other. Accordingly, a space 122f is formed at the position near the open end 121E of the tube 121 and the position near where the annular portion 122B and the disk portion 122A of the cap 122 are connected to each other. Neither the male screw 121C nor the female screw portion 122F are located in the space 122f and the cap 122 and the tube 121 are separated from each other at the space 122f. 
FIG. 3 shows a culture/centrifugal tube 120 with a cap 122′ that is shaped differently from the cap 122 shown in FIG. 2. The cap 122′ includes a disk portion 122A′ and an annular protrusion 122J′. The annular protrusion 122J′ extends from one surface 122C′ of the disk portion 122A′. When the opening portion 121B of the tube 121 is covered by the cap 122′, the annular protrusion 122J′ comes into intimate contact with the opening portion 121B of the tube 121 and seals the opening portion 121B of the tube 121.
Japanese Patent-application Publication Nos. 9-299813 and 7-151661 and Japanese Utility-model Publication No. 5-9653 disclose technology related to culture/centrifugal tubes. In particular, Japanese Patent-application Publication No. 9-299813 discloses a container used for dialysis purposes. The container has an accommodation body and a lid that can be freely attached to and detached from each other by screws provided on their inner and outer peripheral surfaces. Japanese Patent-application Publication No. 7-151661 discloses a phase separation tube having an opening portion at both ends. Japanese Utility-model Publication No. 5-9653 discloses a method of producing a plastic tube in a sealed condition. First, a tube that is to be processed into the container portion is formed with a taper shape at the outer peripheral surface of the opening end. A plug is inserted into the open end of the tube to make an intimate seal.